Many machines include a powertrain for actuating traction devices such as, for example tires. The powertrain typically includes a driveshaft that connects a power source of the machine to a number of axles. The power source typically produces torque to rotate the driveshaft, which in turn provides torque to the axles and the traction devices. Traction forces develop between the traction devices and the ground, allowing the machine to propel itself. The amount of available traction force increases as the weight of the machine increases. Traction devices may slip relative to the ground when the torque transmitted to the traction devices by the power source exceeds the available traction force that can be developed.
For example, when a machine such as a tractor is used to pull a scraper during earthmoving construction, the additional weight of the scraper may greatly increase the traction force that can be developed by the machine. The power source and transmission of the machine may deliver excessive levels of torque to the axles, but not high enough to cause the traction devices to slip. Excessive torque may damage the machine before the traction devices slip.
One attempt at preventing excessive torque is a machine is described in U.S. Pat. No. 3,894,446 (the '446 patent) issued to Snoy et al. The '446 patent discloses a power transmission for a vehicle that has an inter-axel differential for the front and rear axles. The '446 patent discloses that the differential is equipped with a slippable friction clutch that provides a predetermined amount of torque differential for accommodating slipping conditions. The '446 patent also discloses that a torque bias of the friction clutch is determined by the load capacity of the drive train. The friction clutch serves to protect the drive train from excessive loads by slipping when the predetermined torque value is attained. The '446 patent discloses that the friction clutch may be completely released before high speed slip values may cause failure of the clutch.
Although the system of the '446 patent may provide a method for protecting a powertrain from damage due to excessive torque, the system is vulnerable to clutch failure due to high speed slip values. Additionally, the system may not reduce traction of a vehicle, which may increase the possibility of damage to the powertrain.
The present disclosure is directed to overcoming one or more of the problems set forth above.